Glomeruli isolated from normal and diabetic renal cortex will be used for purification of glomerular basement membranes using newer techniques that avoid the use of both ultrasonic disruption and solubilization with proteolytic digestion. These preparations of basement membrane are structurally and chemically intact, and allow identification of specific, presumably authentic components that appear to have similar molecular weights of the order of procollagen. These basement membrane polypeptides will be purified and chemically characterized to determine if differences exist in the amino acid and/or carbohydrate composition of each of these components in diabetes. In vivo studies in which normal and diabetic rats are injected with radiolabeled precursors of collagen and non-collagen sequences of these polypeptides will be performed to detect differences in their incorporation and/or disappearance into these polypeptides or portions thereof, and thereby determine the effect of diabetes on the in vivo biosynthesis and degradation of specific basement membrane components. Short term organic cultures of isolated normal and diabetic rat renal glomeruli will be used to explore biosynthetic processes involved in the production of glomerular basement membrane, with particular reference to the identification and characterization of the initial biosynthetic units and their subsequent modifications. Glomerular incubations with appropriate radiolabeled precursors will also be conducted to determine qualitative and/or quantitative differences in the biosynthesis of each of the basement membrane polypeptides. The effect of diabetes on the intermolecular organization, including disulfide bonds and lysyl-derived crosslinks, will be examined to probe structure-function relationships. The ability to study authentic components of normal and diabetic glomerular basement membranes is expected to resolve the controversy which has surrounded previous comparative compositional studies. Biosynthetic, turnover, and structural studies will provide insight into the pathogenesis of diabetic nephropathy that has eluded satisfactory description.